This invention is for the improvement of the operation of belt-type continuous metal-casting machines. The specification will proceed in terms of describing a twin-belt casting machine as disclosed in U.S. Pat. Nos. 4,588,021 and 3,937,270.
In a thin-gauge-belt-type casting machine, one or more moving, endless, thin, flexible, metallic, water-cooled casting belts successively enter and leave a moving mold cavity. During the casting of molten metal, a flat casting belt is very important. The problem of belt flatness vs. distortion or warping arises because of thermal heat expansion of the belts when the belts enter into contact with molten metal. The casting belt or belts must remain flat and free from distortion or warping, lest the freezing metal lose contact here and there and thereby interrupt the heat transfer locally, causing metallurgical problems. The warping problem is discussed in U.S. Pat. Nos. 3,937,270, 4,537,243 and 4,749,027, all assigned to the same assignee as the present invention.
Insulative, non-wetting belt coverings have been, and continue to be, part of the strategy to eliminate this problem of belt warping or distortion. These include permanent precoverings or base coverings (hereinafter called "basings"). These are described in U.S. Pat. No. 4,588,021 of Bergeron et al. and the more or less temporary top deposits or top dressings or temporary insulative deposits or toppings or mold-release agents, which are applied on top of a basing. All prior-art top or temporary insulative deposits known to us wear and compact and flatten unevenly and thus soon require replenishment or replacement. Manual replenishment of the unevenly worn or flattened spots does not in practice result in re-establishing a top deposit that affords uniform heat transfer. Nor has it been feasible to strip and reapply the prior-art insulative toppings, which usually comprise a binder.
Most of the prior-art top deposits were applied wet. Thus, residues of liquid resulting from such wet applications would sometimes flash into gas and cause porosity or other problems in the cast product. In the casting of copper bar or copper anodes, synthetic oils upon otherwise bare metallic casting belts have been customary, sometimes resulting in similar porosity problems. None of the prior art known to us can achieve the unique results disclosed herein.